While the ball is going up you have a total force of (5*9.8 + 25) N acting against the movement. So you can calculate how long it will take for the velocity to be zero and the corresponding height.
When the ball goes down, there will be a force of (5*9.8 - 25) N accelerating it. Knowing the height the ball starts on, you can calculate the time to reach ground.
edited to add:
The work done by air resistance is the force times the diplacement. Or 25N times twice the height.